Angiogenesis is the process by which cancer tumors develop a network of blood vessels to feed them, so that they may continue their growth. The strategy that cancer cells use to attract blood vessels to them involves a series of chemical messages. Researchers think of this as a type of cellular kidnapping, luring the blood cells with growth factors, which one writer describes as a kind of “biological candy.” According to theory, if cells were treated in a way that they were immune to the lure of the growth factors, then angiogenesis would stop and cancer tumors would die. Much research is going on in this area. However, a Harvard Medical School research team has discovered that things aren’t quite that simple. The relevant proteins, called integrins, are not just responsible for promoting angiogenesis, they also work to turn it off. “The paradigm is emerging that the integrins responsible for angiogenesis are also responsible for stopping it,” said Raghu Kalluri, Harvard Medical School associate professor at Beth Israel Deaconess Medical Center. To block integrins entirely would be to close off the body’s own anti-angiogenic efforts.